Many different designs for icebreaker vessels have been disclosed in the prior art with various features to assist the ice breaking function of the vessel. For example, in U.S. Pat. Nos. 3,931,780 to Waas, and 3,530,814 to Rastorguev et al, a specially designed forecastle is disclosed which includes a wedge-shaped portion and water discharge devices to push broken ice under the surrounding ice layer. The Wass patent also discloses a square bow as well. Also disclosing a square front end and a prow and associated fins for directing broken ice under the surrounding ice layer is U.S. Pat. No. 3,636,904 to Blanchet.
In order to increase the ice breaking ability of ships, various means have been employed. One simple idea has been to merely increase the power output of the engines. Another idea, disclosed in U.S. Pat. No. 2,902,964 to Waas et al, is to provide an increased pitching motion for the icebreaker. Either by shifting water between fore and aft ballast tanks or by swinging weights, the downward breaking motion of the bow on the ice is increased. It has also been disclosed in U.S. Pat. No. 355,214 to Romaine to use reciprocating hammers on either end of a vessel to break or crush the ice into small pieces.
The prior art, however, has failed to provide for an efficient icebreaker which can be used for a variety of different ice thicknesses. In addition, prior art icebreakers simply act to crush the ice layer, which is inefficient and sometimes ineffective when thick ice is encountered.